Answers

Otiorhynchus sulcatus, one of the gardeners nightmares.
They are nasty little grey brown bugs with small cream dots on it's back. The adults nibble away at leaves leaving semi circular notches which is not fatal, but unsigtly. The females don't fly but they do lay their eggs near the top of soil or compost and leave the larvae to hatch and find plant roots to chomp away on. And chomp and kill they will. The larvae are white, c shaped wih a tan dot at the the mouth end. They are found in garden borders, pots in greenhouses , indoors and outside. They especially love strawberry plants.

But don't despair, because you can buy vine weevil killer to water on your pots, but wait until the weather warms up.
The horrid thing about them is they munch the roots quickly and the plant looks healthy, until suddenly it goes flop and you find there are no roots left. They also love cyclamen corms among other things.

Steragram is right. The plant will look sick quite suddenly and very often the whole thing will just come away in your hand. I usually have to dispose of the plant and the compost as it is full of the grubs. I did manage to save a patio rose this year though, by washing the roots and replanting in fresh compost.